1. Field of the Invention
This invention relates to a catalyst useful upon polymerization of an alkylene oxide compound. The present invention is also concerned with a process for producing a poly(alkylene oxide) by polymerizing an alkylene oxide in the presence of an active hydrogen compound and a phosphazene compound or in the presence of a phosphazenium salt of the active hydrogen compound, said phosphazenium salt being derived from the active hydrogen compound and the phosphazene compound. A poly(alkylene oxide) is an important polymer for its utility as a raw material for the production of polyurethane foams and elastomers through its reaction with organopolyisocyanate compounds and also as a surfactant.
2. Description of the Related Art
As practical catalysts for use in the production of a poly(alkylene oxide), basic alkali metal compounds such as potassium hydroxide have found wide-spread utility, for example. Concerning catalysts other than such catalyst, U.S. Pat. No. 3,829,505 discloses obtaining a polymer from propylene oxide in the presence of an initiator while using, for example, a compound represented by Zn.sub.3 Fe(CN).sub.6 !.sub.2 .multidot.H.sub.2 O.multidot.dioxane as a catalyst. Japanese Patent Laid-Open No. 276821/1990 discloses to obtaining a polymer by reacting sodium methylate with a polyol, which has been prepared using zinc hexacyanocobaltate as a catalyst, and polymerizing ethylene oxide in the presence of the reaction product. Further, Japanese Patent Laid-Open No. 232433/1987 discloses to obtain a polymer by polymerizing ethylene oxide while using a reaction product which has been obtained by adding a solution of diethyl zinc in hexane to a dispersion formed by adding 1,4-butanediol and a nonionic surfactant to a slurry of fumed silica in hexane.
It is however known that, when a poly(alkylene oxide) is produced using a metal-containing catalyst such as those described above, a residue of the metal catalyst adversely affects the reaction upon production of polyurethane or physical properties of the resulting polyurethane. A special process or complex steps are therefore needed for the full elimination of such a metal residue upon production of a poly(alkylene oxide).
Concerning metal-free catalysts, on the other hand, Japanese Patent Laid-Open No. 159595/1975 discloses the preparation of a polymer from ethylene oxide while using an ether adduct of boron trifluoride in the presence of an alkanepolyol. This catalyst is however also known to require extremely complex steps for the thorough elimination of its residue and moreover, a particular impurity in the polymer gives deleterious effects on certain physical properties of urethane. Further, according to Japanese Patent Laid-Open No. 12026/1982, a polymer of an alkylene oxide is obtained in the presence of an alcohol while using aminophenol or the like as a catalyst. According to Japanese Patent Laid-Open No. 38323/1981, on the other hand, propylene oxide is polymerized in the presence of sorbitol as an initiator and tetramethylammonium hydroxide as a catalyst. These processes are however accompanied by problems such that the catalysts do not have sufficient polymerization activities and an amine-like odor remains in the resulting polymers.